On Wed, Apr 11, 2012 at 04:37:00PM -0700, Ying Han wrote:> > In 3.2, kswapd was doing a bunch of async writes of pages but> > reclaim/compaction was never reaching a point where it was doing sync> > IO. This does not guarantee that reclaim/compaction was not calling> > wait_on_page_writeback() but I would consider it unlikely. It indicates> > that merging patches 2 and 3 to stop reclaim/compaction calling> > wait_on_page_writeback() should be safe.> >> > include/trace/events/vmscan.h | 40 ++-----> > mm/vmscan.c | 263 ++++-------------------------------------> > 2 files changed, 37 insertions(+), 266 deletions(-)> >> > --> > 1.7.9.2> >> > It might be a naive question, what we do w/ users with the following> in the .config file?> > # CONFIG_COMPACTION is not set>

After lumpy reclaim is removed page reclaim will be reclaiming at order-0randomly to see if that frees up a high-order page randomly. It remains tobe seen how many users really depended on lumpy reclaim like this and asto why they were not using compaction. Two configurations that may care areNOMMU and SLUB. NOMMU may not notice as they were already unable to handleanonymous pages in lumpy reclaim. SLUB will fallback to using order-0 pages.